External device for cleaning filtration material and adapted for application to filtration device

ABSTRACT

An external device for cleaning a filtration material and adapted for application to a filtration device, in which the filtration material can be automatically cleaned easily and at low cost without requiring replacement of an existing filtration device with a newly purchased device. An external device for cleaning a filtration material is applied to a filtration device for filtering a supplied unfiltered liquid by layers of a filtration material to remove muddiness in the liquid and discharging the cleaned liquid to the outside. The cleaning device has an upstanding outer tube, a screw conveyor rotatably placed in the outer tube and transferring the filtration material upward from the lower end to the upper end of the outer tube while rub-washing the filtration material, a drive section for rotationally driving the screw conveyor, a control section for controlling rotation of the drive section, an introduction tube that introduces the filtration material into the outer tube, and a discharge tube for discharging the filtration material, having been rub-washed, into a filtration container from the inside of the outer tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 of PCT/JP2008/001150 filed on May 7, 2008,which claims the benefit of Japanese Patent Application No. 2007-131774filed on May 17, 2007, the contents of each of which are incorporatedherein by reference.

TECHNICAL FIELD

This invention relates to a device for cleaning a filtration material.This invention particularly relates to an external device for cleaning afiltration material and adapted for application to a filtration devicefor removing muddiness in a liquid, such as water, by filtration by useof the filtration material, the external device for cleaning afiltration material being located at the outside of the filtrationdevice.

BACKGROUND ART

In cases where filtration devices are used for a long period of time,filtration sands (filtration materials) within filtration tanks(filtration containers) of the filtration devices are clogged bymuddiness in unfiltered liquids, such as water, it becomes impossible toperform efficient filtration, and quality of the liquid having beenfiltered becomes bad. Therefore, when necessary, the mud substance(muddiness) clinging to the filtration materials is removed, and theclogging of the filtration materials is thereby eliminated. For theaforesaid purposes, it is necessary to perform operations for replacingthe filtration materials, or operations for manually taking out thefiltration materials from the filtration tank, cleaning the filtrationmaterials for peeling off of the muddiness from the filtrationmaterials, and thereafter again returning the cleaned filtrationmaterials into the filtration tanks. In order for the operationsdescribed above to be performed, considerable labor is required, and aspace for cleaning the taken-out filtration materials becomes necessary.Also, in cases where the filtration materials are to be scrapped, largequantities of industrial scraps arise. Therefore, there have heretoforebeen known filtration devices for enabling the aforesaid cleaningoperations to be performed automatically without a large space beingrequired.

As an example of a filtration device capable of cleaning a filtrationmaterial automatically, there has been known a filtration system,wherein a cleaning mechanism (cleaning device) for a filtration materialis located within a filtration tank and is actuated at predeterminedtime intervals, wherein the filtration material is thereby cleaned, andwherein the muddiness having been peeled off the filtration material isdischarged from the filtration tank to the outside (patent literature 1,patent literature 2).

In the filtration system described in the patent literature 1, thecleaning device for cleaning the filtration material by rotation of ascrew conveyor is located on a support plate for supporting layers offiltration sand. Also, the filtration system described in the patentliterature 2 has a constitution, in which the cleaning device forcleaning the filtration material by the rotation of a screw conveyor ishung from an upper section of the filtration tank into the inside of thefiltration tank.

Further, there has been known a filtration sand cleaning system, inwhich a cleaning device is located at the outside of a filtration tank,in lieu of being located at the inside of the filtration tank (patentliterature 3). In the cases of the filtration sand cleaning system,there are disclosed a filtration container provided with a filtrationmaterial, a pump for sucking out the filtration material from thefiltration container, and the filtration material cleaning device forcleaning the filtration material having been sucked out from thefiltration container. In the cases of the cleaning system, the pump isconnected to the filtration tank and the filtration material cleaningdevice respectively by pipes. The filtration system is constituted suchthat the filtration sand containing the muddiness is transferred intothe cleaning device, water is supplied by the pump into the cleaningdevice, and the filtration material from which the muddiness has beenremoved is returned into the filtration tank. Also, the muddiness havingbeen removed is sucked up by a pump from the upper section of thecleaning device and discharged to the outside through piping connectedto the cleaning device.

Patent Literature 1:

PCT International Publication No. WO 01/83076

(FIG. 6)

Patent Literature 2:

Japanese Unexamined Patent Publication No. 2004-160432

(FIG. 1)

Patent Literature 3:

U.S. Pat. No. 5,112,504

(FIG. 1)

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In cases where the user using an existing filtration tank, which is notprovided with a cleaning device, intends to clean filtration sand easilywith a little labor, it is necessary for the entire existing device tobe replaced by a newly purchased filtration device provided with thecleaning device as disclosed in patent literature 1 or patent literature2. In such cases, the problems are encountered in that the cost is notcapable of being kept low.

The filtration system disclosed in patent literature 3 has the problemsin that the filtration system has a complicated shape requiring a largenumber of piping lines and pumps, and in that the operation for cleaningthe filtration material is not of the type for positively cleaning thefiltration material.

In view of the above circumstances, the object of the present inventionis to provide an external device for cleaning a filtration material andadapted for application to a filtration device, wherein the filtrationmaterial is capable of being cleaned easily and at a low cost withoutrequiring replacement of an existing filtration device, which does nothave a cleaning device, with a newly purchased filtration device.

Means for Solving the Problems

The present invention provides an external device for cleaning afiltration material and adapted for application to a filtration device,which filtration device is provided with a filtration container havinglayers of a filtration material at the inside and is adapted forfiltering a supplied unfiltered liquid by the layers of the filtrationmaterial to remove muddiness in the liquid and discharging the cleanedliquid to the outside, the cleaning device comprising:

i) an upstanding outer tube,

ii) a screw conveyor rotatably placed in the outer tube and transferringthe filtration material upward from an inlet at a lower end section ofthe outer tube to an outlet at an upper end section of the outer tube,while rub-washing the filtration material,

iii) a drive section for rotationally driving the screw conveyor,

iv) a control section for controlling rotation of the drive section,

v) an introduction tube, which is connected to the inlet of the outertube and introduces the filtration material from the inside of thefiltration container into the outer tube, and

vi) a discharge tube, which is connected to the outlet of the outer tubeand discharges the filtration material, having been rub-washed, from theinside of the outer tube into the filtration container.

The term “external device for cleaning a filtration material and adaptedfor application to a filtration device” as used herein means thecleaning device capable of being fitted as a post-installed device tothe existing filtration device and embraces both the cleaning device,which is fitted and used only at the time of the cleaning operation, andthe cleaning device, which is installed ordinarily and operated only atthe time of the cleaning operation.

The cleaning device in accordance with the present invention may bemodified such that the screw conveyor is provided with an agitatingblade for agitating the introduced filtration material, which agitatingblade is located at a lower end of the screw conveyor.

Also, the cleaning device in accordance with the present invention maybe modified such that the lower end section of the outer tube, whichlower end section is located at a position corresponding to the positionof the agitating blade, is constituted as a large diameter section.

Further, the cleaning device in accordance with the present inventionshould preferably be modified such that the screw conveyor is providedwith a hollow shaft and a spiral blade, which is formed in a spiralpattern around the hollow shaft, and

the hollow shaft has holes which enable the liquid having beenintroduced into the outer tube to flow from the outside of the hollowshaft into the inside of the hollow shaft.

A plurality of the holes should preferably be formed at a region of thehollow shaft, which region ranges upward from approximately the middlepart of the outer tube, the middle part being taken with respect to thevertical direction. Also, the plurality of the holes should preferablybe formed at intervals of 45° along a circumferential direction of thehollow shaft. Further, a gap between an outer periphery of the spiralblade and an inner surface of the outer tube should preferably beslightly larger than a particle diameter of the filtration material.Furthermore, the spiral blade of the screw conveyor should preferablyextend in a continuous surface pattern from the hollow shaft to aposition in the vicinity of the inner surface of the outer tube. Also,the holes should preferably be located at positions just above thespiral blade.

Effects of the Invention

The external device for cleaning a filtration material and adapted forapplication to a filtration device in accordance with the presentinvention comprises: the screw conveyor rotatably placed in the outertube and transferring the filtration material upward from the inlet atthe lower end section of the outer tube to the outlet at the upper endsection of the outer tube, while rub-washing the filtration material,the drive section for rotationally driving the screw conveyor, thecontrol section for controlling rotation of the drive section, and theintroduction tube and the discharge tube, which tubes are connected tothe outer tube. Therefore, in cases where the user of an existingfiltration device, which is not provided with a cleaning device,purchases only the cleaning device in accordance with the presentinvention and connects the introduction tube and the discharge tube tothe filtration device, the user is capable of automatically cleaning thefiltration material easily and at a low cost. Also, the external devicefor cleaning a filtration material in accordance with the presentinvention is capable of being used without necessity of modification ofthe existing filtration device or with the minimum necessary work beingperformed on the filtration device.

Further, with the cleaning device in accordance with the presentinvention, wherein the screw conveyor is provided with the agitatingblade for agitating the introduced filtration material, which agitatingblade is located at the lower end of the screw conveyor, in cases wherethe liquid (reverse cleaning liquid) containing the filtration materialhaving been introduced into the introduction tube has a highconcentration, i.e. a high viscosity, the filtration material isloosened by the agitation and is capable of being transferred smoothlyby the screw conveyor. Since the concentration of the reverse cleaningliquid is high at the time of the beginning of the reverse cleaningoperation, the agitating blade is particularly useful.

Furthermore, with the cleaning device in accordance with the presentinvention, wherein the lower end section of the outer tube, which lowerend section is located at the position corresponding to the position ofthe agitating blade, is constituted as the large diameter section, thefiltration material having been agitated by the agitating blade isdiffused broadly at the lower end section of the outer tube, at whichlower end section the clogging is ordinarily apt to occur. Therefore,the state of the high concentration (high viscosity) is eliminated moreefficiently, and the filtration material is capable of being transferredmore smoothly by the screw conveyor.

Also, with the cleaning device in accordance with the present invention,wherein the hollow shaft of the screw conveyor, which hollow shaft hasthe spiral blade having been formed in the spiral pattern around thehollow shaft, has the holes which enable the liquid having beenintroduced into the outer tube to flow from the outside of the hollowshaft into the inside of the hollow shaft, the liquid (the reversecleaning liquid) transferred together with the filtration materialupward from the hollow shaft flows through the holes downward into theinside of the hollow shaft. Therefore, the filtration material havingbeen drained is capable of being efficiently transferred upward. If thequantity of water is markedly large, there is the risk that thefiltration material will be merely transferred upward together withwater, and the rub-washing will not be performed sufficiently.

BEST MODE FOR CARRYING OUT THE INVENTION

The external device for cleaning a filtration material and adapted forapplication to a filtration device in accordance with the presentinvention (hereinbelow referred to simply as the cleaning device) willhereinbelow be described in further detail with reference to theaccompanying drawings. FIG. 1 is a schematic vertical sectional viewshowing an embodiment of the cleaning device in accordance with thepresent invention. Also, each of FIG. 2 and FIGS. 3A, 3B is an enlargedview showing a part of a cleaning device 1 of FIG. 1. The cleaningdevice 1 will be described hereinbelow with reference to FIG. 1, FIG. 2,and FIGS. 3A, 3B. Firstly, with reference to FIG. 1, the cleaning device1 comprises a circular cylindrical outer tube 2 made from a metal, ascrew conveyor 4 located within the outer tube 2, and a drive section 6connected to the upper end of the screw conveyor 4. The outer tube 2 isprovided with a flange 8, which is located at the upper end of the outertube 2. A pedestal 12 provided with a flange 10 corresponding to theflange 8 is located on the flange 8. The flange 8 and the flange 10 aresecured to each other by bolts 10 a, and the pedestal 12 is therebysecured to the outer tube 2.

The pedestal 12 is provided with a bearing 14 for supporting a shaft 16of the screw conveyor 4. The bearing 14 is constituted of a bearing 14a, which is located on the side of the flange 10, and a bearing 14 b,which is located midway of the height direction of the pedestal 12. Theshaft 16 of the screw conveyor 4 comprises a hollow shaft 20, which hasa hollow shape, i.e. a pipe-like shape, and which is provided with aspiral blade 18 located within the outer tube 2, and a support shaftsection 22, which is located at the position higher than the hollowshaft 20 and has a diameter slightly smaller than the diameter of thehollow shaft 20. The support shaft section 22 is inserted into thehollow shaft 20 and is secured by welding to the hollow shaft 20. Thesupport shaft section 22 is supported by the bearing 14 described above.A coupling 24 is connected to the upper end of the support shaft section22. The aforesaid drive section 6, which comprises a speed reducingmechanism section 26 and a motor 28 connected to the speed reducingmechanism section 26, is located on the pedestal 12. The motor 28 iselectrically connected to a control section 30 for controlling thenumber of revolutions of the motor 28, which control section may beprovided with, for example, an inverter circuit. In this case, thecontrol section 30 is illustrated in a typical form.

A flange 32 is formed at the lower part of the outer tube 2. A largediameter section 34 is connected by bolts 32 a to the flange 32. Inother words, the lower part of the outer tube 2 is formed as the largediameter section 34. The large diameter section 34 is a circularcylindrical shaped section having a low height and a diameter largerthan a diameter “d” of the outer tube 2. A lower end 4 a of the screwconveyor 4 is located within the large diameter section 34. An inlet 36for introduction of a filtration material 112 a (as illustrated in FIG.4) and a liquid (a reverse cleaning liquid 122 as illustrated in FIG.4), such as water, is formed at a side surface 34 a of the largediameter section 34. An introduction tube 38 is fitted by welding to theinlet 36. In this embodiment, as illustrated in FIG. 1, the introductiontube 38 may be a tube connected with a tube or a hose having anarbitrary shape via a flange 40 into an integral body. Alternatively, asingle long tube, which is not provided with the flange 40, may beemployed as the introduction tube 38. Also, the introduction tube 38 maybe made from a metal, a synthetic resin, rubber, or the like.

Also, an injection hole 42 is formed through a bottom wall 34 b of thelarge diameter section 34. An injection pipe 44 is connected to theinjection hole 42. The injection tube 44 is connected through a flange44 a to a small diameter pipe 46. A ball valve 48 is fitted to the pipe46. At the time of an ordinary state, the ball valve 48 is closed. Whennecessary, the ball valve 48 is opened, and water, or the like, issupplied into the outer tube 2. In cases where the reverse cleaningliquid 122, i.e., a slurry, which contains the filtration material 112 aand the muddiness and which has been introduced from the introductiontube 38, has a high concentration, the injection tube 44 is used todilute the reverse cleaning liquid 122 into a liquid, which is capableof being transferred easily, or is used to inject priming water into theouter tube 2.

Further, an outlet 48 for discharging the filtration material 112 a isformed at the upper end section of the outer tube 2. A discharge tube 50is fitted by, for example, welding to the outlet 48. A ball valve 52 isfitted at a position midway of the discharge tube 50. The ball valve 52need not necessarily be provided in accordance with an applicationexample, which will be described later. Furthermore, a stay 54 forsecuring the cleaning device 1 to, for example, a mounting support (notshown) is fitted to the outer tube 2 so as to extend laterally outwardat a position slightly above a midway part of the outer tube 2, whichmidway part is taken with respect to the vertical direction.

Also, as described above, the part of the shaft 16 of the screw conveyor4, which part extends from the lower end 4 a of the hollow shaft 20 to alower end 22 a of the support shaft section 22, the lower end beinginserted into the hollow shaft 20, is hollow. The intermediate sectionof the hollow shaft 20 is provided with a plurality of holes 56. Theholes 56 will hereinbelow be described with reference to FIG. 1 and FIG.2. FIG. 2 is an enlarged sectional view showing a part of theintermediate section of the outer tube 2 of the cleaning device 1. InFIG. 2, as for the screw conveyor 4, the outer shape thereof isillustrated. The spiral blade 18 of the screw conveyor 4 is formed in aspiral pattern on the outer periphery of the hollow shaft 20. The spiralblade 18 does not have through-holes, slots, or the like, and the entirearea of the surface of the spiral blade 18 constitutes a screw.Therefore, the spiral blade 18 is capable of efficiently transferringupward the reverse cleaning liquid 122 containing the filtrationmaterial 112 a.

It is set such that a slight gap G is formed between an outer periphery,i.e. an outer edge 18 a, of the spiral blade 18 and an inner surface 2 aof the outer tube 2. In cases where the particle diameter of thefiltration material 112 a falls within the range of, for example, 0.6 mmto 1.0 mm, the dimension of the gap G is set to be slightly larger thanthe particle diameter. The reasons are as described below. Specifically,at the time at which the filtration material 112 a is transferred upwardby the screw conveyor 4, the filtration material 112 a is moved towardthe outer periphery of the spiral blade 18 by centrifugal force arisingdue to the rotation of the screw conveyor 4. However, the filtrationmaterial 112 a is prevented by the aforesaid gap G from being squeezedand ground between the outer edge 18 a of the spiral blade 18 and theinner surface 2 a of the outer tube 2 at the time of the rub-washing.Also, since the filtration material 112 a and the peeled-off muddinessexist at the gap G, the degree of sealing between the screw conveyor 4and the outer tube 2 is enhanced, and the efficiency of transfer of thefiltration material 112 a and the reverse cleaning liquid 122 isenhanced.

The aforesaid holes 56 are formed so as to be located just above thefitting section of the spiral blade 18 to the hollow shaft 20. Since theholes 56 are located just above the spiral blade 18, the reversecleaning liquid 122 stagnating on the spiral blade 18 is capable ofsmoothly flowing along the spiral blade 18 into the holes 56. Theplurality of the holes 56 are formed over two pitches of the spiralblade 18 and at a rate of one hole per 45 degrees along the fittingsection. The cleaning device 1 is installed such that the positions ofthe holes 56 are higher than the level of the reverse cleaning liquidwithin the filtration tank to be cleaned. Since the inside of the hollowshaft 20 is hollow, a part of the reverse cleaning liquid 122, which isbeing transferred upward from the holes 56, is capable of flowing intothe hollow section. The holes 56 described above have the effects ofdraining of the reverse cleaning liquid 122 which is transferred. Thenumber of the holes 56 and the intervals of the holes 56 along thecircumference of the hollow shaft 20 are not limited to those in theaforesaid embodiment and may be altered appropriately in accordance withthe use applications.

The shape of the lower end section of the screw conveyor 4 will bedescribed herein below with reference to FIG. 1, FIG. 2, and FIGS. 3Aand 3B. FIGS. 3A and 3B are enlarged views showing the lower end sectionof the screw conveyor 4. FIG. 3A is a front view, and FIG. 3B is abottom view. As illustrated in FIGS. 3A and 3B, the agitating blade 58is fitted to the lower end 4 a of the hollow shaft 20 of the screwconveyor 4. The agitating blade 58 is constituted of four ribs 58 ahaving an identical length. The ribs 58 a are constituted by combiningtwo metal plates, each of which has a length of a dimension larger thanthe diameter of the hollow shaft 20, in a cross-shaped pattern. Also,the agitating blade 58 is fitted by welding to the lower end 4 a of thehollow shaft 20, such that the center point of the cross-shaped pattern,i.e. an intersection point 58 b of the two metal plates, and a rotationcenter point 16 b of the shaft 16 may coincide with each other.Therefore, the hollow section of the hollow shaft 20 is in communicationwith the outside.

In cases where the reverse cleaning liquid 122, i.e., the slurry, whichcontains the filtration material 112 a and which has been introducedinto the cleaning device 1, has a high concentration, the agitatingblade 58 is utilized for agitating the filtration material 112 a andthereby preventing the filtration material 112 a from stagnating at thelower part in the outer tube 2. Therefore, in cases where theconcentration of the liquid is low, the agitating blade 58 need notnecessarily be provided. For example, the agitating blade 58 may bemerely omitted. Alternatively, the lower end 4 a may have a closedshape.

Application examples, in each of which the cleaning device 1 having beenconstituted in the manner described above is applied to an existingfiltration tank, will be described hereinbelow with reference to FIG. 4,FIG. 5, and FIG. 6. The term “filtration device” as used herein meansthe entire device including the filtration tank and other subsidiaryfacilities, such as a support leg. FIG. 4 illustrates a firstapplication example. FIG. 5 and FIG. 6 illustrates a second applicationexample. Firstly, an application example, in which a cleaning device 1 ais applied to a filtration tank 101 of a filtration device 100, will bedescribed hereinbelow with reference to FIG. 4. The different embodimentof the cleaning device 1 a used in this case has a constitutionbasically identical with the constitution of the aforesaid cleaningdevice 1, except for the positions and the shapes of a discharge tube 50a and an introduction tube 38 a. Also, the cleaning device 1 a isdifferent from the cleaning device 1 of FIG. 1 in that the largediameter section 34 at the lower part of the outer tube 2 and theagitating blade 58 are not provided. At a lower end of a shaft 16′ of ascrew conveyor 4′ of the cleaning device 1 a, the opening of the shaft16′ is sealed by, for example, a cap 60. The cleaning device 1 a issupported by an appropriate support 70. In FIG. 4, similar parts withrespect to the parts in FIG. 1 are explained by use of the samereference number. Also, parts which need not be explained are attachedwith the reference numbers of principal parts corresponding to theembodiment of FIG. 1, and the explanation of the parts is omitted.

The filtration tank 101 has, as a typical shape, a circular cylindricalouter shell body 102, whose upper section and a lower section are closedrespectively by curved convex surfaces. The filtration tank 101 issupported by a support leg 103. An unfiltered water injection port 104for injection of water containing the muddiness, i.e. the unfilteredwater, is formed at an upper part of a side surface of the outer shellbody 102. A discharge port 106 is formed at a lower part of the outershell body 102. Also, a large diameter manhole 118 is formed at theupper surface of the outer shell body 102.

As an example of the filtration tank 101, as illustrated in FIG. 4, aplate 110, which is provided with strainers 114, is located within theouter shell body 102, and layers 108 of gravel 108 a having largeparticle diameters are located at positions upward from the plate 110.Also, layers 112 of a filtration material 112 a, such as sand havingsmall particle diameters, are located on the layers 108 of the gravel108 a up to a level 112 b. The unfiltered water is injected from theunfiltered water injection port 104, passes through the layers 112 ofthe filtration material 112 a and the layers 108 of the gravel 108 awithin the filtration tank 101, and is thus filtrated. A cleaned liquid,from which the muddiness has been removed, passes through the strainers114, and is supplied from the discharge port 106 to the outside.

In the cases of the filtration tank 101 constituted in the mannerdescribed above, wherein the opening section of the manhole 118 iscomparatively large, as illustrated in FIG. 4, a discharge tube 50 a andan introduction tube 38 a may be inserted through the manhole 118, andthe existing filtration tank 101 is thus capable of being used withoutbeing modified and altered.

How the filtration material 112 a in the filtration tank 101 is cleanedafter the filtration tank 101 and the cleaning device 1 a have beeninstalled in the manner described above will be described hereinbelow.At the time of the ordinary filtration, the height of the filtrationmaterial 112 a coincides with a level 112 b. At the time, at which thefiltration is ceased, and the reverse cleaning is performed at thepreliminary stage of the cleaning, the reverse cleaning liquid 122expands and rises up to, for example, an opening 107 a of an inside tube107, which opening is located at a height indicated by a level 120.Specifically, in cases where the cleaning liquid 122 is injected fromthe discharge port 106 for the reverse cleaning into the filtration tank101, the reverse cleaning liquid passes through the strainers 114 andthe layers 108 and is jetted out to the layers 112, and the filtrationmaterial 112 a expands and flows. However, the filtration material 112 adoes not fly high up to the liquid surface of the reverse cleaningliquid 122 having expanded to the level 120 and flows at most up to alevel 109, which is located at the position slightly higher than thelevel 112 b. The liquid located at the positions lower than the level109 constitutes a slurry (a suspension). Therefore, the filtrationmaterial 112 a is distributed through the slurry, and the distributiondensity of the filtration material 112 a becomes low. However, themuddiness having been peeled off by the reverse cleaning from thefiltration material 112 a is lighter than the filtration material 112 aand therefore flows up to the level 120.

In the state described above, the motor 28 is actuated. In the cases ofthe application example described above, wherein the position of thescrew conveyor 4′ is higher than the position of the level 120 of theliquid surface of the reverse cleaning liquid 122, the reverse cleaningliquid 122 is not capable of being easily sucked into an outer tube 2′only by the rotation of the screw conveyor 4′. Therefore, it isnecessary for the priming water to be injected from an injection tube44′. The motor 28 is thereafter actuated, and the reverse cleaningliquid 122 and the filtration material 112 a in the filtration tank 101are capable of being easily introduced into the outer tube 2′.

The filtration material 112 a having been introduced into the lower partof the outer tube 2′ is transferred upward while being rub-washed by thespiral blade 18 of the screw conveyor 4′. While the filtration material112 a is thus being transferred upward, the filtration material 112 a iscleaned, and the muddiness is peeled off from the filtration material112 a. The filtration material 112 a having thus been cleaned passesthrough the discharge tube 50 a and is discharged into the filtrationtank 101 together with the reverse cleaning liquid 122 containing thepeeled-off muddiness. Since the filtration material 112 a does not flowin the region between the level 109 and the level 120 of the slurry,only the reverse cleaning liquid 122 containing the muddiness flows outfrom the aforesaid inside tube 107. At this time, the reverse cleaningliquid 122 is continuously injected from the discharge port 106 into thefiltration tank 101, and therefore the reverse cleaning liquid 122containing the muddiness is continuously discharged from the aforesaidinside tube 107 to the outside. Therefore, the quantity of the muddinesscontained in the reverse cleaning liquid 122 circulated within thefiltration tank 101 and the cleaning device 1 a decreases little bylittle. The control section 30 is operated in order to set the number ofrevolutions of the screw conveyor 4′ at a value appropriate for therub-washing. For example, in the cases of the screw conveyor 4′ having aradius of 10 cm, the number of revolutions of the screw conveyor 4′should preferably be set such that the circumferential speed of theouter edge 18 a of the screw conveyor 4′ may become equal to at most 4m/sec.

After the muddiness in the filtration tank 101 has been removed throughiteration of the aforesaid process for a predetermined period of time,the introduction tube 38 a and the discharge tube 50 a are taken out.The ordinary filtration operation thus becomes capable of beingperformed. The cleaning device 1 a may be ordinarily installed at apredetermined position in the vicinity of the filtration tank 101.Alternatively, only when necessary, the cleaning device 1 a may beinstalled in the vicinity of the filtration tank 101. After the cleaningby the cleaning device 1 a has been completed, the reverse cleaning maybe continued for a certain period of time, and the muddiness in thereverse cleaning liquid may thereby be discharged.

A second application example of a further different embodiment of thecleaning device in accordance with the present invention will bedescribed hereinbelow with reference to FIG. 5 and FIG. 6. FIG. 5 is avertical sectional view showing a cleaning device. FIG. 6 is a schematicplan view showing a filtration tank, the view illustrating a position ofa discharge tube located in a filtration tank 201. A cleaning device 1 billustrated in FIG. 5 has a constitution approximately identical withthe constitution of the cleaning device 1 illustrated in FIG. 1, exceptfor the position and the shape of a discharge tube 50 b. Also, forclearness, the control section 30 is not illustrated. Further, afiltration tank 201 of a filtration device 200 is based upon a principleidentical with the principle of the filtration tank 101. Therefore, onlyprincipal parts of the filtration tank 201 are explained, and detailedexplanations of the filtration tank 201 are omitted. Furthermore, ascrew conveyor 4″ has the shape identical with the shape of the screwconveyor 4′ illustrated in FIG. 4. In the cases of the secondapplication example, slight reconstruction is necessary for the existingfiltration tank 201. Reconstruction includes the provision of a fittingsection 222 for the discharge tube 50 b at an upper part of an outershell body 202, and the provision of a fitting section 224 for anintroduction tube 38 b at an approximately middle part with respect tothe height of the outer shell body 202. In the cases of the filtrationtank 201, the liquid level at the time of the reverse cleaning coincideswith the height indicated by 220 in FIG. 5. Also, the lower end section,i.e. the large diameter section 34, of the cleaning device 1 b isconnected to the fitting section 224 by the introduction tube 38 b,which is approximately horizontal. Therefore, the region of an outertube 2″, which region extends from the middle point with respect to theheight direction of the outer tube 2″ to the part downward from themiddle point, is located at the position lower than the level 220.Therefore, at the time of the reverse cleaning, the reverse cleaningliquid 122 enters from the introduction tube 38 b up to the middle pointof the outer tube 2″. Accordingly, in the cases of the secondapplication example, the priming water need not be used. As in the firstapplication example, the actuation of the motor 28 is performed at thetime of the reverse cleaning. In the cases of the filtration tank 201,the discharging of the reverse cleaning liquid 122 is performed througha horn-shaped inside tube 226, which communicates with the outside ofthe filtration tank 201.

As illustrated in FIG. 5 and FIG. 6, the length of the discharge tube 50b is set to be long. Also, as illustrated in FIG. 6, the discharge tube50 b is located so as to extend along the circumference of the inside ofthe filtration tank 201. In such cases, the reverse cleaning liquid 122discharged from the discharge tube 50 b flows out along the innercircumference of the filtration tank 201 as indicated by the arrows. Bythe stream of the reverse cleaning liquid 122, the filtration material112 a is agitated, the slurry uniformly containing the filtrationmaterial 112 a is introduced into the introduction tube 38 b, and thecleaning effect is enhanced even further.

In the application example illustrated in FIG. 5 and FIG. 6, the fittingsection 222, at which the discharge tube 50 b is located, takes theposition on the side identical with the side of the fitting section 224,at which the introduction tube 38 b is located. Alternatively, thefitting section 222, at which the discharge tube 50 b is located, maytake the position on the opposite side of the filtration tank 201, i.e.on the side remote from the fitting section 224, at which theintroduction tube 38 b is located. In such cases, the filtrationmaterial 112 a discharged from the discharge tube 50 b enters into thefiltration tank 201 from the position spaced away from the fittingsection 224, and therefore the slurry having not been cleaned is easilyintroduced into the cleaning device 1 b. The aforesaid feature isobtained also in the application example illustrated in FIG. 4 and inthe application example, which will be described later. Also, thedischarge tube 50 b should preferably be made from a flexible material.

A modification of the application example illustrated in FIG. 5 and FIG.6 will be described hereinbelow with reference to FIG. 7 and FIG. 8. InFIG. 7 and FIG. 8, similar elements are numbered with the same referencenumerals with respect to FIG. 5 and FIG. 6, and detailed explanations ofthe similar elements are omitted. FIG. 7 is a vertical sectional viewcorresponding to FIG. 5, and FIG. 8 is a schematic plan viewcorresponding to FIG. 6. The modification varies in that a leading endsection 50 b′ of the discharge tube 50 b is constituted of a metal tube.Therefore, the leading end section 50 b′ is directly fitted to thefiltration tank 201 by welding and is thus combined with the filtrationtank into an integral body. The metal discharge tube 50 b′ is thussecured in the closed state to the filtration tank 201. Therefore, atthe time at which the ordinary filtration is performed, the inside ofthe filtration tank 201 is capable of being filled with the unfilteredwater without the discharge tube 50 b being taken out, and theworkability is thus capable of being kept good. Also, the advantages areobtained in that the service life of the discharge tube 50 b′ is long,and in that the position at which the discharge tube 50 b′ is installeddoes not alter.

A third application example of a still further different embodiment ofthe cleaning device in accordance with the present invention will bedescribed hereinbelow with reference to FIG. 9. In FIG. 9, forclearness, the control section 30 is not illustrated. Also, a screwconveyor 4X has a shape identical with the shape of the screw conveyor4′ illustrated in FIG. 4. In this application example, such that theworkability of the cleaning device, which is ordinarily located at aposition higher than the filtration tank, may be enhanced, the cleaningdevice is located at a low position. A filtration tank 301 of afiltration device 300 used in this application example has aconstitution approximately identical with the constitution of thefiltration tank 101 used in the first application example, except for aslight modification. Specifically, the filtration tank 301 is modifiedsuch that an introduction tube 38 c is fitted to a side surface of thefiltration tank 301. A cleaning device 1 c itself is located at a lowposition close to a floor 3. The introduction tube 38 c is connectedfrom the side surface of the filtration tank 301 to a lower end sectionof the cleaning device 1 c and extends obliquely downward from the sidesurface toward the lower end section. A discharge tube 50 c is locateddownward from an upper part of an outer tube 2X of the cleaning device 1c. The reverse cleaning liquid 122 containing the cleaned filtrationmaterial discharged from the discharge tube 50 c is stored in afiltration material storing container 80. The filtration materialstoring container 80 is provided with a filtration material pump 82. Thefiltration material having been stored is discharged by the filtrationpump (sand pump) 82 through a hose 84, which acts as a discharge tube,into a manhole 318 of the filtration tank 301. In other words, in thethird application example, the discharging is performed from thedischarge tube 50 c via the filtration material pump 82. Thisapplication example has the advantages in that, as described above,since all of the work is capable of being performed at the low position,the workability is kept good.

In each of the aforesaid embodiments and the aforesaid applicationexamples, the cleaning device is constituted for the cleaning of thefiltration sands. However, the object of the cleaning is not limited tothe sands and may be, for example, other filtration materials, such asanthracite, activated carbon, and a mixture of the above-enumeratedfiltration materials. Also, as the liquid to be filtered, theexplanation has been made with respect to water. However, the liquid tobe filtered may be one of other liquids, such as an oil.

Further, in the third application example, the pump intervenes at theposition midway of the discharge tube 50 c. Also, a pump for sucking thefiltration material 112 a, or the like, may intervene at a positionmidway of the introduction tube 38, 38 a, or 38 b.

INDUSTRIAL APPLICABILITY

The external device for cleaning a filtration material and adapted forapplication to a filtration device in accordance with the presentinvention is capable of being used by being applied to an existingfiltration tank.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic vertical sectional view showing an embodiment ofthe external device for cleaning a filtration material and adapted forapplication to a filtration device in accordance with the presentinvention,

FIG. 2 is an enlarged view showing a part of the external device forcleaning a filtration material and adapted for application to afiltration device illustrated in FIG. 1,

FIG. 3A is an enlarged front view showing a part of the external devicefor cleaning a filtration material and adapted for application to afiltration device illustrated in FIG. 1,

FIG. 3B is an enlarged bottom view showing a part of the external devicefor cleaning a filtration material and adapted for application to afiltration device illustrated in FIG. 1,

FIG. 4 is a vertical sectional view showing a first application exampleof a different embodiment of the external device for cleaning afiltration material and adapted for application to a filtration devicein accordance with the present invention,

FIG. 5 is a vertical sectional view showing a second application exampleof a further different embodiment of the external device for cleaning afiltration material and adapted for application to a filtration devicein accordance with the present invention,

FIG. 6 is a schematic plan view showing a part of the external devicefor cleaning a filtration material and adapted for application to afiltration device illustrated in FIG. 5,

FIG. 7 is a vertical sectional view showing a modification of theapplication example illustrated in FIG. 5 and FIG. 6,

FIG. 8 is a schematic plan view showing a part of the modification ofthe application example illustrated in FIG. 5 and FIG. 6, and

FIG. 9 is a vertical sectional view showing a third application exampleof a still further different embodiment of the external device forcleaning a filtration material and adapted for application to afiltration device in accordance with the present invention.

The invention claimed is:
 1. An external device for cleaning afiltration material having a particle diameter in the range of 0.6 mm to1.0 mm and adapted for application to a filtration device, whichfiltration device is provided with a filtration container having anupper layer of a filtration material at the inside and is adapted forfiltering a supplied unfiltered liquid by the layers of the filtrationmaterial to remove muddiness in the liquid and a discharge port fordischarging the cleaned liquid to the outside, in which reverse cleaningliquid, is injected into the discharge port when the reverse cleaning ofthe filtration material is performed, the cleaning device comprising: i)a substantially vertically oriented upstanding outer tube, ii) a screwconveyor rotatably placed in the outer tube and transferring thefiltration material upward from an inlet at a lower end section of theouter tube, rub-washing the filtration material to separate muddinessfrom the filtration material, and transferring the separated muddinessand filtration material to an outlet at an upper end section of theouter tube, wherein the screw conveyor is provided with a hollow shaftand an imperforate spiral blade for rub-washing the filtration materialby the rotation thereof, which is formed in a spiral pattern around thehollow shaft, wherein a gap is formed between an outer edge of thespiral blade and an inner surface of the outer tube that is slightlylarger than the particle diameter of the filtration material to preventsqueezing and grinding of the filtration material between the outer edgeof the spiral blade and the inner surface of the outer tube and toenhance a degree of sealing between the outer edge of the spiral bladeand the inner surface of the outer tube caused by a presence offiltration material and peeled-off muddiness existing at the gap duringrub-washing, the hollow shaft has holes which enable the liquid havingbeen introduced into the outer tube to flow from the outside of thehollow shaft into the inside of the hollow shaft, and the spiral bladeis fixed to the hollow shaft whereby the spiral blade rotates with thehollow shaft, iii) a drive section for rotationally driving the screwconveyor, iv) a control section for controlling rotation of the drivesection to move the filtration material toward an outer periphery of theblade by centrifugal force and to transfer the filtration material andreverse cleaning liquid upwardly toward to the outlet, v) anintroduction tube, one end of which is connected to the inlet of theouter tube and the other end of which is located at the upper layer ofthe filtration material to introduce the filtration material and thereverse cleaning liquid from the inside of the filtration container intothe outer tube, and vi) a discharge tube which is connected to theoutlet of the outer tube and discharges the filtration material, havingbeen rub-washed and the reverse cleaning liquid, from the inside of theouter tube into the filtration container.
 2. An external device forcleaning a filtration material and adapted for application to afiltration device as defined in claim 1 wherein the screw conveyor isprovided with an agitating blade for agitating the introduced filtrationmaterial, which agitating blade is located at a lower end of the screwconveyor.
 3. An external device for cleaning a filtration material andadapted for application to a filtration device as defined in claim 2wherein the lower end section of the outer tube is located at a positionof the agitating blade, is constituted as an enlarged diameter section.